1. Field of the Invention
The present invention relates generally to a magnetic tape cassette in which a front lid is pivotably mounted on the cassette housing so as to selectively open or close a front opening portion for a tape path of the cassette housing in order to protect a magnetic tape from being damaged. More particularly, this invention relates to a magnetic tape cassette of the sort as described above which is suitable for accommodating therein a magnetic tape on and/or from which a PCM (pulse-code-modulated) signal is recorded and/or reproduced.
2. Description of the Prior Art
FIGS. 1 and 2 are illustrations, respectively, of a conventional magnetic tape cassette in which a magnetic tape for a PCM signal is accommodated.
As FIG. 1 shows, a cassette housing 1 is comprised of an upper section or half 11a and a lower section or half 1b, which are secured together by suitable conventional means such as screws. A pair of reel hubs 2a and 2b are mounted rotatably in the cassette housing 1, and a magnetic tape 3 is wound on the pair of reel hubs 2a and 2b. A front lid 4 is pivotably mounted on the cassette housing 1 so as to selectively open or close the front opening portion of the cassette housing 1.
Now, FIG. 1 shows the state in which the front opening portion of the cassette housing 1 is closed by the front lid 4. The front lid 4 comprises a lid main section 4a and a pair of side supporting sections 4b. The lid main section 4a has a rectangular configuration having a length and width sufficient so that it can close the entire front opening portion of the tape cassette. The pair of side supporting sections 4b are elongated from both side ends of the lid main section 4a and bent backwards at a right angle. The side supporting sections 4b respectively each have a shaft aperture which is rotatably supported by a shaft 6 formed at a predetermined position on each side wall of the cassette housing. The front lid 4 is made of a plastic material having sufficient flexibility or elasticity so that when it is warped toward the cassette housing side, it can be engaged with the front opening portion of the cassette housing 1 due to its elastic deformation, thus being halted at a predetermined position to close the front opening portion of the cassette housing 1.
FIG. 2 illustrates the conventional magnetic tape cassette of this example which is ready for recording or reproduction. As FIG. 2 shows under this condition, the front lid 4 is opened manually or automatically by an automatic lid opening and/or closing mechanisms (not shown) of a tape recorder or the like and the magnetic tape 3 is exposed in the front opening portion of the cassette housing 1.
As described above, the magnetic tape cassette of this example is provided with the front lid 4 so that without a specially-prepared cassette case, upon non-use, as illustrated in FIG. 1, the front opening portion of the cassette housing 1 is closed by the front lid 4 so as to protect the magnetic tape 3 in the front opening portion from being touched by fingers or the like. Also, by the front lid 4, dust, smudges and the like can be prevented from entering the main body of the magnetic tape cassette.
In the thus arranged magnetic tape cassette, when the front lid 4 is in its opened state, the lid main section 4a is released from being engaged with the front opening portion of the tape cassette and restored to the former state with the result that the side supporting sections 4b of the front lid 4 would both be detached from the side walls of the cassette housing 1. Thus, the front lid 4 is allowed to freely move in the direction perpendicular to its rotation direction, i.e., in the axial direction of the shafts 6. If this movement of the front lid 4 is increased, the front lid 4 may be detached away from the cassette housing 1.
Further, upon use, the front lid 4 is opened under the condition that the tape cassette is loaded onto a recording and/or reproducing apparatus. Thus, when the front lid 4 is moved in the axial direction of the shafts 6 and protruded from both side walls of the cassette housing 1, the protruded portions of the front lid can be accidentally caught somewhere within the recording and/or reproducing apparatus. There is then a risk that the tape cassette may not be ejected from the recording and/or reproducing apparatus.
Furthermore, since in the conventional magnetic tape cassette the front lid 4 is pivotably secured to the cassette housing 1 at its side supporting portions 4b by the shafts 6 and both the shafts 6 have the same diameter, the front lid 4 can be pivotably secured to the cassette housing 1 even in a reversed condition. In such a case when the front lid 4 is constructed such that it is asymmetrical with respect to the up and down direction or right and left direction, if the front lid 4 is pivotably secured to the cassette housing in its reversed condition, this results in an inferior magnetic tape cassette.
In addition, since stopper edge surfaces, with which the side supporting portions 4b and 4c of the front lid 4 are brought in contact when the front lid 4 of the cassette housing 1 is opened are formed perpendicularly to the upper and lower surfaces of the cassette housing when the front lid 4 is closed, relatively large spacings are respectively brought about between the stopper edge surfaces and the side supporting portions 4b and 4c as shown in FIG. 1. Accordingly, lid-opening-pins provided in the recording and/or reproducing apparatus for opening the front lid 4 tend to accidentally drop into the spacing between the stopper edge surfaces of the cassette housing 1 and the end edges of the side supporting portions 4b, 4b of the front lid 4. Thus, the tape cassette is prevented from moving back and forth so that the ejection as well as the recording and/or reproduction will not be made.